[iOS] Remove background color for text in TableViewImageItem

Removing the background color for image view, and the text cell.

Before:
https://drive.google.com/open?id=1T01IhXHKK-CwBjijghpBRYkRwPWxoMEj
After:
https://drive.google.com/open?id=1_IeyemBl9mptpUZoTTqiTESy7Nnbl8bV

Bug: 984985
Change-Id: I0fbcbf392dfc177ca42ac1828bbd84a285df7220
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1706696
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678344}

ios/chrome/browser/ui/table_view/cells/table_view_image_item.mm

@@ -45,11 +45,6 @@
 
   cell.textLabel.text = self.title;
   cell.detailTextLabel.text = self.detailText;
-  UIColor* cellBackgroundColor = styler.cellBackgroundColor
-                                     ? styler.cellBackgroundColor
-                                     : styler.tableViewBackgroundColor;
-  cell.imageView.backgroundColor = cellBackgroundColor;
-  cell.textLabel.backgroundColor = cellBackgroundColor;
   if (self.textColor) {
     cell.textLabel.textColor = self.textColor;
   } else if (styler.cellTitleColor) {